Abstract: To study the strong interaction effect between internal weapon bay and missile during the weapon release, the unsteady flow around a simplified weapon bay and missile model is simulated using SST k-ω improved delayed detached eddy simulation (IDDES) method, six-degrees-of-freedom rigid body dynamics equations and overset mesh method. The fluctuation of pressure in the weapon bay is analyzed using the smooth pseudo Winger-Vile distribution (SPWVD) method, and the time-frequency characteristics of pressure are obtained. The research results show that, when a missile is delivered from the weapon bay, the shear layer is destroyed to lead to the change in the flow structure, the self-sustained oscillation disappears in the weapon bay, and there is no obvious cavity tone. Stronger vortexes concentrate in the trailing edge of cavity, and thus the sound pressure level (SPL) in the trailing edge of the weapon bay increases. After the missile is delivered from the weapon bay, the shear layer is rapidly reestablished and the self-sustained oscillation shows up again. The impact of the accelerated flow near the head of the missile leads to enhance the instability in shear layer. Accordingly, the sound pressure level in the weapon bay is enhanced. The missile flies at a large angle of attack since it is affected by upward force moment during passing through the shear layer. After the missile is delivered from the weapon bay, it begins to be affected by vertical upward force and pitch down moment. The vertical upward force can hinder the missile from falling. Meanwhile, the force and moment acting on the missile fluctuate strongly under the effect of the unsteady flow in the weapon bay.

Key words: fluid mechanics, internal weapon bay, weapon release, overset mesh, SST DES model, smooth pseudo Winger-Vile distribution